With the increasing down-scaling of integrated circuits (ICs) and increasingly demanding requirements to the speed of ICs, transistors need to have higher drive currents with increasingly smaller dimensions. Fin field-effect transistors (FinFETs) were thus developed. In a FinFET, portions of a substrate are etched away to create a vertical fin structure. This vertical fin structure is used to form source/drain regions in the lateral direction, forming a channel region in the fin. A gate is formed over the fin in the vertical direction, thus forming a FinFET.